Once we learned that, we went to some area lakes to see how clean they are.

The holiday weekend had already started at Boone Lake, as dozens of swimmers were jumping in to get out of the heat.

"Really busy, really crowded," described Paige Jarrett.

Jarrett has been going to the swimming area at Boone Dam her whole life. She told us, sometimes, swimmers aren't the only ones in the water.

"A lot of scrap wood or driftwood but I have seen bottles, band-aids, plastic stuff, cups and stuff like that," said Jarrett.

It's something that could get worse with more people heading out over the next few days.

South Holston Lake was busy with boaters, as they crisscrossed each other. We talked to Bristol, Tennessee's Utility Services manager David St. John to find out whether more people at the lake could cause water contamination.

Bristol Tennessee's water comes from the South Holston River, downstream from the lake.

"You can have 10 times the amount of people out there and that does not affect us in any way shape or form," said St. John.

He told us the serious bacteria doesn't come from trash but from animals, and when sediments get kicked up.

"You've got animals out there that go to the restroom, you've got birds flying over so you could have a mix of all kinds of different things coming from the raw water," St. John said.

He told us runoff during bad storms can also cause pollutants to flow into the river but that the summer rainstorms we've been having still aren't big enough to cause major contamination.

Despite all of that, the river's levels are completely normal, said St. John.

We talked to Johnson City's Water and Sewer Services on Thursday as well since their water comes from Watauga River.

They told us they do not see effects of holiday recreation in their contamination levels.

Even though we found out it is safe to swim in many of our area lakes and rivers, it may not be safe to fish in all of them. There are fish tissue advisories across Northeast Tennessee.

To see the full list of advisories, you can visit the Tennessee Wildlife Agency's website.